1. Field of the Invention
The present invention relates to a method and system for reducing or removing a foam in a glass melting furnace, and in particular to a method and system for reducing or removing a foam formed during a glass melting process.
2. Description of the Related Art
A glass melting furnace is conventionally used to melt an initial raw material to form a molten material which can be subsequently processed into a glass product. For example, the molten material can be used to form glass fibers. Such glass fibers can be used, for example, in insulation and structural reinforcement applications. In addition to glass fibers, the molten material provided by a glass melting furnace can be used to form, for example, flat glass, glass containers and various specialty glass products.
During the melting of the initial raw material introduced into the glass melting furnace, a foam is typically formed above the molten material in the furnace. The foam can be formed from the evolution of gas during the melting of the initial raw material. Generally, the foam contains small bubbles held together by a matrix of molten material, and forms a layer over at least a part of the surface of the molten material. The physical characteristics of such foam layer can depend on the conditions in the furnace. Foam layer thickness, for example, typically can be from about 2 inches (5.1 cm) to about 4 inches (10.2 cm).
The presence of foam can impede the transfer of heat from a heat source of the glass melting furnace, to the initial raw material and/or the molten material present underneath the foam. In conventional systems, the heat source typically must therefore provide an additional amount of heat in order to compensate for the insulating effect of the foam. As a result, the presence of the foam can increase the operating costs of the glass melting furnace. Further, the increased temperature in the furnace can shorten the operating life of the furnace and/or increase the production of particular exhaust gases such as, for example, NOx gases and toxic metal oxide gases.
In light of the above, reducing the foam in a glass melting furnace can be advantageous at least because such reduction can result in an increase in energy efficiency. For example, it has been estimated that the cumulative impact of removing about half of the foam in U.S. combustion-heated glass furnaces could result in an annual energy savings of as much as 12 to 14 trillion BTU. Further, abating the foam in a furnace can extend furnace life as well as reduce the production of particular exhaust gases.
Reducing or removing the foam present above the molten material in a glass melting furnace can be difficult to achieve. For example, various attempts at foam abatement including adjusting the glass chemistry (e.g., by using chemical additives in the initial raw material) and varying the furnace crown heating profile, have been ineffective and/or unpredictable. In addition, using an oxygen rich combustion heat source in place of an air combustion heat source can actually result in an increase in foam generation.
In view of the foregoing, an object of the present invention is to provide a method and system of reducing or removing a foam present in a glass melting furnace. Other objects and aspects of the present invention will become apparent to one of ordinary skill in the art upon review of the specification, drawings and claims appended hereto.
According to one aspect of the present invention, a method for reducing or removing a foam present in a glass melting furnace is provided. The method comprises providing an ultrasonic energy emitted from at least one ultrasonic energy source to a foam present above the surface of a molten material in a glass melting furnace, wherein the ultrasonic energy is effective to selectively reduce or remove at least a part of the foam.
According to another aspect of the present invention, a system for reducing or removing a foam present in a glass melting furnace is provided. The system comprises at least one ultrasonic energy source for providing an ultrasonic energy to a foam present above the surface of a molten material in the glass melting furnace, wherein the ultrasonic energy is effective to selectively reduce or remove the foam.